A slide member such as a slide bearing used for example in an automobile engine is provided with an overlay for improving fatigue resistance and seizure resistance. The overlay is provided over a bearing alloy layer made for example of materials such as a copper alloy which is in turn provided over a metal back. A soft Pb alloy was conventionally used as the overlay. However, due to its heavy environmental load, replacement of Pb with Bi or Bi alloy is being suggested in recent years. Because Bi is relatively brittle, various countermeasures have been conceived to overcome such brittleness.
For instance, JP H11-50296 A discloses improving the sliding properties by adding one or more types of elements from Sn, In, and Ag to an overlay composed of Bi. JP 2003-156046 A discloses improving the wear resistance by adding hard particles such as borides, silicides, oxides, nitrides, etc. of metals to an overlay employing Bi or Bi alloy. JP 2001-20955 A and JP 2004-308883 A disclose improving the sliding properties by controlling the crystal plane of Bi constituting the overlay to a specific orientation. Further, JP 2003-156045 A discloses improving the fatigue resistance by controlling the density of precipitate particles of Bi constituting the overlay.
As described above, various ideas have been conceived for improving the sliding properties of slide members in which Pb used in the overlay is replaced by Bi-based (Bi or Bi alloy) materials. Attempts for further improvement of engine performance subjects slide members, assembled to components such as connecting rods, to further rigorous working environment. Thus, further improvement of sliding member performance, especially seizure resistance improvement, is required.